Here is Day 19: Interfaces problem solution in Python, Java, C++ C and javascript - https://programmingoneonone.com/hackerrank-day-19-interfaces-30-days-of-code-solution.html

Hardly an exercise in Abstractions/Interfaces.

c# conditional operator

public int divisorSum(int n) { int sum=0;

    for(int i=1;i*i<=n;i++)
    {
        var q=Math.DivRem(n,i,out int r);

        if(r==0)
        {
            sum+=i!=q?i+q:i;
        }
    }

    return sum;
}

c#

public int divisorSum(int n) { int sum=0;

    for(int i=1;i*i<=n;i++)
    {
        var q=Math.DivRem(n,i,out int r);

        if(r==0)
        {
            sum+=i;

            if(i!=q)
            {
                sum+=q;
            }
        }
    }

    return sum;
}

In Java 8

import java.io.; import java.util.; interface AdvancedArithmetic{ int divisorSum(int n); } class Calculator implements AdvancedArithmetic { public int divisorSum(int n) { int sum=0; for(int i=1;i<=n;i++) { if(n%i==0) sum+=i; } return sum; } }